I don’t follow your line of reasoning here and am bewildered where the so-called regress erupts. To attempt an answer to your question in brief however, God can still be pure actuality because His essence, in its subsumption of all moments, is eternally situated in transcendence, above time, albeit with localized aspects “appearing” in the fabric of time, immediately out-distanced and out-traversed by God’s having already “scaled” (an imperfect verb, as it implies time) the evolutes produced by time.
In brief, it is a separate question to say whether there is potentiality “in” God and whether God is pure act unmixed with potentiality.
Thanks for participating Psychlo!
In my thinking, an infinite causal regress for the situation I just described erupts as follows:
I. God has a potential which can be actualized. (This is false, but is assumed for the sake of the argument)
II. It is impossible for a potential to actualize itself, but a cause must actualize it.
III. The cause that actualizes a potential must be itself actual, and not potential. (otherwise that cause doesn’t really exist, but only exists as a potential cause, it only might exist).
IV. An actual cause actualizes this potential that God has; this cause would then need to be either (X). some distinct ‘part’ of God that is actual and not potential, or (Y). some other (non-temporally) prior cause that isn’t God but is actual and not potential, a “super-God” or “meta-God”. (by prior I mean higher in the chain of causality, not further back in time).
V. (X). and/or (Y) Are either purely actual, or are some mixture of actual or potential.
VI. If (X) and/or (Y) are some mixture of actual and potential then they themselves need an actual part of themselves (XX), or a distinct (non-temporally) prior actual cause (YY) to actualize their potential.
VII. (XX) and/or (YY) must themselves either be purely actual, or some mixture of actual or potential.
VIII. If (XX) and/or (YY) are some mixture of actual or potential, then they themselves need an actual part of themselves (XXX) or a distinct (non-temporally) prior actual cause (YYY) to actualize their potential.
IX. Steps V through VIII repeat as many times as you like, but not infinitely (or else an infinite causal regress occurs, where every part needs another part needs another part (ad infinitum) or every distinction (nontemporally) prior actual cause needs another distinct prior actual cause needs another distinct prior actual cause (ad infinitium).
X. Eventually, then, you must arrive at a “part” (Xprime) and/or a distinct, (non-temporally) prior actual cause (Yprime) that are themselves entirely actual, and have no mixture of potentiality in them.
XI. Let this fully and purely actual ‘part’ or ‘cause’, which has within it no potential to be actualized, be called “God-prime”.
Change my statement that you disagreed with originally to say instead:
"Is there any potential in God-prime? If yes, God-prime is not pure actuality, but rather has a potential which cannot be actualized outside of time. There must then be some purer actuality to actualize this potential, but that purer actuality too would itself need to have the potential to actualize the less-pure-actuality’s potential. (Leading to an infinite causal regress, which is logically impossible).
To any readers, please note: The above explanation was purely hypothetical, there is no higher God, and God is the highest being and is pure actuality, and has no parts in His substance, but is simple. All that the Church in Her Magisterium teaches as a matter of Faith regarding God is true, and nothing I say above is correct if it contradicts any of Her infallible teaching.